This investigation is designed to achieve a greater understanding the chemistry of technetium, and to use this knowledge in the rational design of new radiopharmaceuticals incorporating the radionuclide 99mTc. Beginning with already characterized compounds in well-defined oxidation states complexes will be prepared, isolated and studied using methods which have been successfully applied to the coordination chemistry of other transition metals. The aim of the synthetic program is to give a profile of the oxidation state, stereochemistry, nature of the bonding and the relative ligand affinities of technetium compounds. As the systematics of the element's behavior emerge, this information will be applied to the designing and synthesizing of materials which show potential as radiodiagnostic agents. These will then be evaluated in appropriate animal models.